Perineal Muscles
Perineal muscles form the pelvic floor, supporting pelvic organs and enabling continence.
The perineal muscles are a group of skeletal muscles located in the superficial and deep layers of the perineum. They are involved in urogenital function, sexual activity, defecation, and support of pelvic viscera. These muscles are organized into two primary groups based on their location relative to the perineal membrane: superficial and deep perineal muscles. They differ between males and females but share a common structural and functional framework.
Structure
The perineal muscles are arranged around the urogenital and anal openings, forming slings and sphincters that control bodily functions and maintain pelvic integrity. They are innervated primarily by the **pudendal nerve (S2–S4)** and are supplied by branches of the **internal pudendal artery**.
Superficial Perineal Muscles
- Bulbospongiosus:
- Males: Covers bulb of penis; aids in erection and expulsion of urine/semen
- Females: Surrounds vaginal orifice; compresses greater vestibular glands
- Ischiocavernosus: Covers crura of penis or clitoris; helps maintain erection by compressing venous return
- Superficial transverse perineal muscle: Extends from ischial tuberosity to perineal body; stabilizes perineal body
Deep Perineal Muscles
- External urethral sphincter: Encircles urethra; allows voluntary urinary continence
- Deep transverse perineal muscle: Stabilizes perineal body and supports pelvic floor
- Compressor urethrae and sphincter urethrovaginalis (in females): Assist in urethral compression during continence
Anal Triangle Muscle
- External anal sphincter: Voluntary sphincter of the anal canal; maintains continence
Location
Perineal muscles are located in the perineum, divided between the urogenital and anal triangles. They are organized into two pouches separated by the perineal membrane:
| Muscle Group | Location |
|---|---|
| Superficial perineal muscles | In the superficial perineal pouch (between Colles' fascia and perineal membrane) |
| Deep perineal muscles | In the deep perineal pouch (between perineal membrane and pelvic diaphragm) |
| External anal sphincter | Surrounds the anal canal in the anal triangle |
Function
- Urinary continence: External urethral sphincter and compressor urethrae regulate urine flow
- Sexual function: Ischiocavernosus and bulbospongiosus aid in erection and ejaculation (males), and vaginal compression (females)
- Pelvic support: Transverse perineal muscles and sphincters stabilize the perineal body and support pelvic organs
- Fecal continence: External anal sphincter maintains anal closure
Clinical Significance
- Perineal tears: Common during childbirth; may involve superficial or deep muscles
- Pelvic floor dysfunction: Weakness or damage to perineal muscles may cause incontinence or organ prolapse
- Episiotomy: Involves cutting superficial perineal muscles to facilitate delivery
Last updated on May 11, 2025
